diff --git a/include/boost/throw_exception.hpp b/include/boost/throw_exception.hpp
index 3f06fcd..97a2695 100644
--- a/include/boost/throw_exception.hpp
+++ b/include/boost/throw_exception.hpp
@@ -1,8 +1,8 @@
 #ifndef BOOST_THROW_EXCEPTION_HPP_INCLUDED
 #define BOOST_THROW_EXCEPTION_HPP_INCLUDED
 
-#if _MSC_VER >= 1020
-#pragma once
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
 #endif
 
 //